The present invention relates generally to articulated dental chairs and more particularly to a dental chair wherein articulation of the back, seat and footrest sections are accomplished in synchronism upon operation of a single motor.
Dental chairs are known in which the back, seat and footrest sections are articulated relative to each other upon actuation of a single motor. For example, as the backrest is moved from an upright to a reclined position, it is desirable to simultaneously elevate the footrest and to tilt the chair slightly. This permits the dentist to smoothly translate the patient through all operative positions while minimizing excessive positioning decisions on his part.
Further, it is desirable to have the backrest pivoted at a location simulating the theoretical hip joint of the patient. In most chairs, the center of rotation of the chairback doesn't coincide with the center of rotation of the patient's back (the hip joint). As a result, during inclination of the backrest, the curve traced by a point on the back of the patient's head, does not coincide with a curve traced by a corresponding point on the headrest of the chair. The headrest thus appears to pull away from the patient's head during inclination and causes discomfort to the patient. When fully inclined, the patient must readjust his position for his comfort and to enable the dentist to work more effeciently. When the chairback rotates back up, because of the patient's new position, the chairback tends to "pinch" the patient in the lower back region.
Under the pivoting conditions described in this invention, the curve traced by a point on the back of the patient's head, does coincide with the corresponding point on the headrest. As such, there is no discomfort to the patient while being positioned into the supine position, no need for the patient to readjust when supine, and no discomfort to the patient when being returned to the upright position.